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- 2. Arthropods form a huge assemblage of small coelomate animals with “jointed limbs” (hence the name arthro-pods).
- 3. (a) Digestive system The alimentary canal comprises three distinct regions: the foregut or stomodium, the midgut
- 4. (c) Respiratory system In the vast majority of insects, respiration is by means of internal air
- 5. (e) Excretory System The function of the excretory system is to maintain hemostasis. i.e. maintaining the
- 6. Biodiversity The main arthropod assemblages include crustaceans (crabs, lobsters, crayfish, shrimp), arachnids (spiders, scorpions, ticks, mites)
- 7. Insects have 3 distinct body parts, commonly called the head, thorax and abdomen. The head has
- 8. Collectively, arthropods account for a substantial share of global biodiversity, both in terms of species richness
- 9. Life cycles Adult arthropods are generally small in size, most are visible but some remain microscopic.
- 11. Arthropods are involved in nearly every kind of parasitic relationship, either as parasites themselves or as
- 12. Direct
- 13. (larva or adult parasitic)
- 14. (all feeding stages parasitic)
- 15. Direct transmission of infective stages occurs when hosts come into close contact with each other or
- 16. Taxonomic overview 1. Insects exhibit extraordinary biodiversity, both in terms of species richness (numbers of species)
- 17. Flies and mosquitoes are winged insects with two pairs of wings attached to the thorax and
- 18. Lice are small wingless insects, dorsoventrally flattened, with reduced or no eyes and enlarged tarsal claws
- 19. Ticks are epidermal parasites of terrestrial vertebrates that may cause anaemia, dermatosis, paralysis, otoacariasis and other
- 20. Mites are microscopic arachnids which undergo gradual or incomplete metamorphosis. Adults and nymphs have 4 pairs
- 21. Importance of Arthropods in parasitology Arthropods affect the health of man by being: 1. Direct agents
- 22. 2. Agents for disease transmission Arthropods can carry disease causative agents in the following two ways.
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Arthropods form a huge assemblage of small coelomate animals with “jointed
Arthropods form a huge assemblage of small coelomate animals with “jointed
General characteristic
The arthropods include animals varying considerably in size and shape but have fundamental features in common. Generally all arthropods have the following characteristics in common:
• They are bilaterally symmetrical, have a body cavity called haemocele, which contains haemolymph (blood and lymph) that bathes internal organs.
• They exhibit segmentation of their bodies (metamerism) which is often masked in adults because their 10-25 body segments are combined into 2-3 functional groups (called tagmata). They have jointed appendages, which may take the form of legs, antennae, or mouthparts.
• They have a hard chitinous exoskeleton (cuticle), which helps for the protection and insertion of muscles. Arthropods possess a rigid cuticular exoskeleton consisting mainly of tanned proteins and chitin. The exoskeleton is usually hard, insoluble, virtually indigestible and impregnated with calcium salts or covered with wax. The exoskeleton provides physical and physiological protection and serves as a place for muscle attachment. Skeletal plates are joined by flexible articular membranes and the joints are hinges or pivots made from chondyles and sockets.
Arthropods use the following systems for survival and perpetuation.
(a) Digestive system
The alimentary canal comprises three distinct regions: the foregut
(a) Digestive system
The alimentary canal comprises three distinct regions: the foregut
(b) Circulatory system
The circulatory system of all arthropods is of the “open” type, i.e. the fluid that circulates is not restricted to a network of conducting vessels as for example in vertebrates, but flows freely among the body organs. A consequence of the open system is that insects have only one extra cellular fluid, hemolymph, in contrast to vertebrates which have two such fluids, blood and lymph. Through this system hemolymph is pumped from the heart to the aorta then to the whole body. The circulatory system has no respiratory function.
(c) Respiratory system
In the vast majority of insects, respiration is by
(c) Respiratory system
In the vast majority of insects, respiration is by
(d) Nervous system
They exhibit varying degrees of cephalization whereby neural elements, sensory receptors and feeding structures are concentrated in the head region.The many diverse activities of the various systems of an insect are coordinated by the nervous system.
This system is composed of elongated cells, or neurons, which carry information in the form of electrical impulses from internal and external sensory cells to appropriate effectors. These consist of Nerve ganglia in the head, ventral part of the body, which later extends to body parts.
(e) Excretory System
The function of the excretory system is to maintain
(e) Excretory System
The function of the excretory system is to maintain
(f) Reproductive System
Arthropods have separate sexes. Male contains testes, vas deference, seminal vesicle and ejaculatory duct, which open by aedeagus (penis). The female contains two ovaries, oviduct, and uterus that opens to the vagina.
Biodiversity
The main arthropod assemblages include crustaceans (crabs, lobsters, crayfish, shrimp), arachnids
Biodiversity
The main arthropod assemblages include crustaceans (crabs, lobsters, crayfish, shrimp), arachnids
Insects have 3 distinct body parts, commonly called the head, thorax
Insects have 3 distinct body parts, commonly called the head, thorax
Arachnids have 2 body parts known as the prosoma (or cephalothorax) and opisthosoma (or abdomen). The cephalothorax has 8 legs arranged in 4 bilateral pairs and arachnids do not have wings or antennae. Important parasitic assemblages include the ticks and mites which bite into tissues and feed off host fluids.
Collectively, arthropods account for a substantial share of global biodiversity, both
Collectively, arthropods account for a substantial share of global biodiversity, both
Life cycles
Adult arthropods are generally small in size, most are visible
Life cycles
Adult arthropods are generally small in size, most are visible
Arthropods are involved in nearly every kind of parasitic relationship, either
Arthropods are involved in nearly every kind of parasitic relationship, either
Direct
Direct
(larva or adult parasitic)
(larva or adult parasitic)
(all feeding stages parasitic)
(all feeding stages parasitic)
Direct transmission of infective stages occurs when hosts come into close
Direct transmission of infective stages occurs when hosts come into close
Many adult insects actively seek hosts in order to feed or lay eggs. Winged insects (mosquitoes, flies) fly to new hosts to feed while fleas jump onto passing hosts. Some adult flies (botflies) do not feed on their hosts but deposit eggs from which larvae emerge and feed on host tissues and exudates.
Tick larvae actively seek hosts by climbing vegetation and questing for passing hosts. Some species complete their life-cycle on the same host (one-host ticks) while others detach after feeding and drop to the ground to moult before seeking new hosts as nymphs or adults (two-host or three-host ticks).
Taxonomic overview
1. Insects exhibit extraordinary biodiversity, both in terms of species
Taxonomic overview
1. Insects exhibit extraordinary biodiversity, both in terms of species
Fleas are bilaterally-flattened wingless insects with enlarged hindlimbs specially adapted for jumping (up to 100 times their body length). Jumping feats are accomplished using elastic resilin pads which expand explosively when uncocked from the compressed state. Fleas undergo complete metamorphosis whereby grub-like larvae form pupae from which adult fleas emerge. The larvae are not parasitic but feed on debris associated mainly with bedding, den or nest material, whereas the adult stages are parasitic and feed on host blood. There are some 2,500 flea species, most parasitic on mammals (especially rodents) and some on birds. They vary in the time spent on their hosts ranging from transient feeders (rodent fleas) to permanent attachment (sticktight fleas and burrowing chigoes).
Flies and mosquitoes are winged insects with two pairs of wings
Flies and mosquitoes are winged insects with two pairs of wings
Lice are small wingless insects, dorsoventrally flattened, with reduced or no
Lice are small wingless insects, dorsoventrally flattened, with reduced or no
2. Many non-spider Arachnids (subclass Acari) are found as parasites on animal or plant hosts. They belong to two main groups: the macroscopic ticks and the microscopic mites. Many species are important in human and animal medicine as causes of disease or as transmission vectors for other pathogens.
Ticks are epidermal parasites of terrestrial vertebrates that may cause anaemia,
Ticks are epidermal parasites of terrestrial vertebrates that may cause anaemia,
Mites are microscopic arachnids which undergo gradual or incomplete metamorphosis. Adults
Mites are microscopic arachnids which undergo gradual or incomplete metamorphosis. Adults
Importance of Arthropods in parasitology
Arthropods affect the health of man by
Importance of Arthropods in parasitology
Arthropods affect the health of man by
1. Direct agents for disease /discomfort.
The following effects may be seen by the direct effect of arthropods.
• Annoyance – comes from disruptive activities of insects, such as flying around or landing on the head, and from feeding, possibly causing blood loss, though they don’t remove sufficient blood to cause a medical problem in humans.
• Entomophobia – is an irrational fear of insects. One extreme form of entomophobia is delusory parasitosis, in which individuals become convinced that they are infested with insects when no actual infestation exists. This may cause undue alarm and anxiety, leading to unwarranted use of insecticides, and in severe cases, requiring professional treatment.
• Envenomization – is the introduction of a poison into the body of humans and animals. Arthropods may also inoculate poison to the host. E.g. Scorpion
• Allergic reactions – a hypersensitive response to insect proteins. All of the mechanisms associated with envenomization can also cause exposure to allergens. In fact, human deaths from bee and wasp stings usually are associated with a hypersensitive reaction rather than direct effect of a toxin.
• Dermatosis and dermatitis – dermatosis is a disease of the skin and dermatitis is an inflammation of the skin. Both dermatosis and dermatitis can be caused by arthropod activities. Many mite species, such as scabies mites produce acute skin irritations.
2. Agents for disease transmission
Arthropods can carry disease causative agents in
2. Agents for disease transmission
Arthropods can carry disease causative agents in
a) Mechanical carrier
Here they lodge the disease causative agent without altering its development or multiplication e.g. house fly
b) Biological carrier
When arthropods become biological carriers for transmission of disease, it means that certain stages in the life cycle of parasite take place in the body of the insect. e.g. Anopheles mosquitoes. Biological carrier is any of the following types:
Propagative – where there is multiplication of the parasite with no developmental change e.g. Yellow fever virus in Aedes mosquito.
Cyclopropagative – in this type both multiplication and developmental change are going on. e.g. Plasmodium species in Anopheles mosquito
Cyclodevelopmental – here there is developmental change of the parasite but no multiplication E.g. Wucherera bancrofiti in Culex mosquito
Transovarian – when the pararasite passes to progeny arthropods through the ova E.g. Ricketsia typhi in ticks